Various stereotactic surgery instruments have been known. For example, Leksell Frame is used as a manual stereotactic surgery instrument for brain surgery. Leksell Frame has a structure in which a user is able to manually move the stereotactic surgery instrument along X, Y, and Z-axes and is able to rotate the same such that the position of the stereotactic surgery instrument corresponds to the position of an affected portion. However, in the case of using such a manual stereotactic surgery instrument, since the user should read gradations on the Leksell Frame with the naked eye to then determine and move the position of the surgery instrument, it tends to cause an error between the position of the affected portion and the surgery instrument.
Therefore, a technology for utilizing a robot for the stereotactic surgery has been introduced in order to improve the accuracy of positioning the surgical instrument. The stereotactic surgery robot is implemented with a robot arm that includes a driving arm assembly, wherein the robot arm is coupled to a fixed base and includes a plurality of arms that are connected in series. The position of the surgical instrument that is attached to the serial type of robot arm and the surgical accuracy thereof may be affected by all axes of the robot arm with a degree of freedom. That is, when an error occurs in the operation by using one axis of the robot arm, the error is added to another error that occurs in the operation by using another axis so that the errors caused by all axes are accumulated to then affect the surgical accuracy. In this case, when an operational error occurs at the driving end that is installed on the base, the error is added to other operational errors of a plurality of robot arms that are connected to the base so that the error is further amplified as it goes to the end of the robot arm. Therefore, in order to improve the surgical accuracy, it is preferable to set the distance between the base to which the robot arm is fixed and the affected portion to be short. However, if the distance between the base of the robot arm and the affected portion is shortened, the inertia of the robot arm becomes small. Therefore, an error tends to occur, and thus, it is difficult to make precise control of the robot arm. In addition, since a space between the base of the robot arm and the affected portion becomes small, the operating range of the robot arm may be reduced. In addition, in the case where the robot arm fixed to the base is disposed around the affected portion, there may be a risk that the user may collide with the robot arm when the user moves around the affected portion so that the movement of the user may be disrupted.
Meanwhile, the position of a surgical target and the entry position (or entry) of the surgical instrument should be specified for stereotactic surgery. In the case of brain surgery or nerve surgery, if the entry position of a surgical instrument is not properly set, the surgical instrument may come into contact with critical portions of the brain or nerves prior to approaching a surgical target in order to thereby put the patient in unnecessary danger. However, the conventional stereotactic surgery instrument is controlled in a state in which the movement of the surgical instrument according to the position of a surgical target is not independently separated from the movement of the surgical instrument according to the entry position of a surgical instrument. Therefore, if an error occurs between the actual position of the surgical instrument and the position of the surgical instrument, which is recognized by the stereotactic surgery robot system, the control of the surgical instrument for correcting the error may be complicated.